AMMAN, Feb 23 (Reuters) - At least 14 people were killed and 70 wounded in a car bombing on Sunday near a field hospital in a Syrian town on the border with Turkey that serves as a main supply line for rebels fighting President Bashar al-Assad, activists said.

The attack shattered relative calm in a region of far northern Syria that has been a safe haven for thousands of refugees fleeing the three-year civil war.

The bomb exploded in the town of Atmeh, situated amid olive groves opposite the Turkish village of Bukulmez in the province of Hatay. The target was a hospital owned by Ghassan Abboud, a pro-opposition businessman who owns Orient Television.

Orient Television, based in Dubai and broadcasting into Syria, has been vehement in its criticism of the Islamic State of Iraq and the Levant (ISIL), an al Qaeda splinter group that has seized several strategic areas along the border and choked supply lines to more moderate rebel groups in the interior.

Atmeh has been held by a loose coalition of Islamist rebels, including al-Nusra front and The Islamic Front, who drove out the ISIL fighters from the town two months ago.

A doctor at a state hospital in Reyhanli across the border in Turkey, a strong backer of the Syrian rebels, said several wounded Syrians were brought there, some in critical condition.

"The façade of the hospital was blown off. Most of the casualties were transported to Bab al-Hawa (crossing) and to another hospital in Atmeh. Some of the worst cases reached Turkey," said witness Abdallah Saleh.

Zakwan al-Hadid, an opposition activist in Idlib said the attack looks to have been the work of the ISIL. "Orient has been relentless in criticising the ISIL and the ISIL had already kidnapped several Orient journalists. The regime also stands to benefit from a safe haven like Atmeh being targeted."

Orient Foundation, a humanitarian network run by Abboud, said patients, doctors and nurses were among the casualties.

"This barbaric attack took place against a hospital that treats the wounded from the bombs of death the regime is using on liberated areas. Orient Foundation accuses the Assad regime of being behind the attack," an Orient statement said.

Tens of thousands of people have been killed since the revolt against Assad erupted in March 2011 with pro-democracy demonstrations. It turned to a militarised uprising in response to a violent crackdown by Assad's security forces.

Now, Islamist fighters, including jihadis from across the world, have eclipsed secular groups and are also at war with each other in much of Syria, with the Nusra Front and other Islamists fighting the ISIL - a group disavowed by al Qaeda.

(Additional reporting and writing by Mariam Karouny in Beirut; Editing by Mark Heinrich)

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